Tropospheric Emissions: Monitoring of Pollution (TEMPO) has been selected by NASA as the first Earth Venture Instrument. The Smithsonian Astrophysical Observatory will build an instrument to measure atmospheric pollution for greater North America from space. On an hourly basis TEMPO will measure atmospheric pollution from Mexico City to the Canadian tar/oil sands, and from the Atlantic to the Pacific. TEMPO will provide measurements that include the key elements of air pollution chemistry, such as ozone, nitrogen dioxide and sulfur dioxide, in the lowest part of the atmosphere. Measurements will be from geostationary (GEO) orbit, to capture the inherent high variability in the daily cycle of emissions and chemistry. Measuring across both time and space will improve emission inventories, monitor population exposure, and enable effective emission-control strategies.